This invention relates to a process and an apparatus for preparing a composition using a continuous extruder. More particularly, this invention relates to a process and an apparatus for preparing a composition by feeding a slurry from a slurry vessel into a continuous reactor.
Heretofore, chemical compositions, for example polymers, have been prepared using continuous reactor extruders. For example, U.S. Pat. No. 4,612,355 discloses the use of extruders for the manufacture of plastics. More specifically, U.S. Pat. No. 4,612,355 discloses the use of reaction extruders to prepare epoxy resins.
Typically, the feed of reactants to such extruders is carried out as solids and or as a melt prior to feeding the extruder. It is difficult to thoroughly and intimately mix the solids together before or while feeding the solids to an extruder. Some chemicals cannot be fed as solids and must be prepared in a different manner.
In addition, feed accuracy demands for continuous processes are high, particularly when the continuous process is plug flow, with minimum backmixing, and a step polymerization. Step polymerizations involving two different di-functional feeds, represented by Axe2x80x94A and Bxe2x80x94B, where A reacts with B, are very sensitive to the ratio of Axe2x80x94A and Bxe2x80x94B regarding final molecular weight and physical properties.
Generally, liquid feeds are preferred for step polymerization processes, as a feed accuracy of less than 0.1% can be achieved using liquid feeds. However, in some manufacturing processes, one or more of the feeds must be a solid, because a liquid feed form may not be desirable due to degradation or safety concerns. Thus, a solid feed system, such as a loss-in-weight feeder, is required when a liquid feed can not be used. The accuracy of loss-in-weight feeders can approach 0.25% over a one minute interval, but is generally greater than 1% over a 5 second interval. It would be advantageous to avoid having to use a solid feed systems in processes which can not accurately handle solids.
It is therefore desired to provide a process and apparatus for preparing a composition using a slurry feed to a reactor such as an extruder. More preferably, it is desired to provide a process and apparatus which allows averaging of the short term accuracy of a solids feeder by holding up several minutes worth of feed in a continuously stirred, backmixed vessel in combination with a liquid feed.
The present invention pertains to a process and an apparatus for preparing compositions from one or more resinous materials and other ingredients using a continuous reactor combined with a continuous slurry feed apparatus for feeding the slurry feed stream to the reactor.
In one specific embodiment of the present invention, the present process and apparatus prepares a composition by feeding a slurry of one or more monomers and/or oligomers into a continuous reactor to manufacture one or more resinous materials. The resinous materials may optionally be combined with other additives in a mixer or recovered as a flake for further use.
This process integrates a slurry feeding operation with a reactive extrusion operation. The present invention avoids problems associated with raw materials feed rate variation when using a solid additive to a liquid material without having to melt the solids. The present invention advantageously provides accurate feed flow from a solids feeder.